不同形狀絕熱多邊形管之熱傳特性分析

The analysis of heat-transfer characteristics for the insulated polygonal pipes with different shapes

盧廷祥(Hsiang-Ting Lu)

指導教授 ： 黃景良

崑山科技大學/工程學院/機械工程研究所/碩士(2005年)

https://doi.org/10.6828/KSU.2005.00051

摘要

本文使用一維的平面楔型熱阻(Plane Wedge Thermal Resistance, PWTR )模型和平板熱阻( Plate Thermal Resistance , PTR)模型，來分析絕熱多邊形管的熱傳特性，並與由CFD軟體FLUENT所得之二維數值結果作比較。本文發現，絕熱多邊形管使用PWTR模型所得熱傳率的誤差率均為正值，而以PTR模型所得的熱傳率的誤差率均為負值; 為抵消其正負誤差，本文應用混合ㄓ騍v的PWTR模型以及β比率的PTR模型之組合平板與楔形熱阻(CPWTR)模型，求出可得較準確的熱傳率各種形狀相對之ㄓ峉]值。因此，可得各種形狀多邊形管之簡單可靠一維CPWTR模型，以作為工程對絕熱多邊形管快速熱傳分析之用。此外，本文對於小尺寸的臨界熱傳特性，亦進行了深入探討，探討微小絕熱多邊管的臨界厚度和中性厚度等等現象，以及決定其是否需包覆絕熱材料與否。此外，本文並對很小絕熱多邊形管之臨界熱傳現象作深入的探討，發現小絕熱多邊形管之臨界厚度(或等週長絕熱正多邊形管之內切絕熱圓管的臨界半徑)隨著其不同邊數之多邊形管而有不同的值。

關鍵字

PWTR模型 ； PTR模型 ； 臨界半徑 ； CPWTR模型 ； 絕熱 ； 多邊形管

並列摘要

The heat-transfer characteristics of the insulated polygonal pipes are analyzed by using the one-dimensional Plane Wedge Thermal Resistance (PWTR) model and Plate Thermal Resistance (PTR) model in this study. It is found that the errors generated by the PWTR model are all positive and the errors generated by the PTR model are all negative in comparison with the two-dimensional numerical solutions obtained by the CFD software. The Combined Plate Wedge Thermal Resistance (CPWTR) model generated by paralleling PWTR and PTR models with the proportion factors of ?vs. β can neutralize the positive and negative errors and thus the more accurate results can be obtained. The suitable values of ?and β for different shapes of insulated polygonal pipes have been found in this study and they can be apply to the simple and reliable engineering analysis. Additionally, this study also investigates the critical heat-transfer phenomenon for the insulated polygonal pipes with very small size. It is found that the critical values of insulated thickness (or critical radius of insulated circular pipe inscribed to the equivalent perimeter insulated regular polygonal pipe) of the insulated polygonal pipes are different with their edge-number.

並列關鍵字

polygonal pipe ； insulation ； PWTR model ； PTR model ； CPWTR model ； critical radius

參考文獻

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